The present invention relates generally to the field of electronic data storage and retrieval, and in particular to an improved writer in a merged giant magnetoresistance (GMR) read/write head.
A GMR read/write head generally consists of two portions, a writer portion for storing magnetically-encoded information on a magnetic disc and a reader portion for retrieving magnetically-encoded information from the disc. The reader portion typically consists of a bottom shield, a top shield, and a giant magnetoresistive (GMR) sensor positioned between the bottom and top shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a free layer of the GMR sensor, which in turn causes a change in electrical resistivity of the GMR sensor. The change in resistivity of the GMR sensor can be detected by passing a current through the GMR sensor and measuring a voltage across the GMR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
The writer portion typically consists of a top and a bottom pole, which are separated from each other at an air bearing surface of the writer by a gap layer, and which are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. Positioned between the top and bottom poles are one or more layers of conductive coils encapsulated by insulating layers. The writer portion and the reader portion are often arranged in a merged configuration in which a shared pole serves as both the top shield in the reader portion and the bottom pole in the writer portion.
To write data to the magnetic media, an electrical current is caused to flow through the conductive coils to thereby induce a magnetic field across the write gap between the top and bottom poles. By reversing the polarity of the current through the coils, the polarity of the data written to the magnetic media is also reversed. Because the top pole is generally the trailing pole of the top and bottom poles, the top pole is used to physically write the data to the magnetic media. Accordingly, it is the top pole that defines the track width of the written data. More specifically, the track width is defined by the width of the top pole near the write gap at the air bearing surface.
In magnetic recording, it is desirable to improve the areal density at which information can be recorded and reliably read. This desire has lead to a trend toward shorter bit length along a magnetic recording track and a shrinking track width. Narrow track widths are achieved by use of narrow pole tips at an air bearing surface (ABS) of the head. However, the pole width must be large in the paddle region of the head where the coil passes between the poles. The larger pole width is necessary to gain adequate magnetic flux through the poles by the coil write current. Hence, it is common to taper the pole from the larger width in the paddle region to a narrower width in the pole tip region at the ABS.
The length of the bit cell is largely dictated by a length of the write gap. The gap length is defined as the length between opposing pole tips at the ABS along the length of a recorded track. The gap height, commonly referred to as the throat height, is the distance from the ABS to a xe2x80x9czero throat positionxe2x80x9d, where both of the pole tips converge at the write gap. Typically, the throat height is 1 or 2 micrometers and is defined in part by the position of a zero throat insulator. The zero throat insulator is used not only for zero throat height definition, but also to improve efficiency of the recording head. The thickness of the zero throat insulator is typically about 1-2 micrometers.
Prior art configurations have a distinct limitation in that the top pole is typically formed over the zero throat insulator, resulting in the top pole having a xe2x80x9cbumpxe2x80x9d shape. The portion of the top pole adjacent the air bearing surface in prior art configurations is sloped. It is therefore difficult to precisely control the width of the top pole at the air bearing surface, particularly as the width necessarily becomes smaller to allow for greater data storage densities. Since the pole tip is formed on the zero throat insulator, which requires a thick photoresist process with a very high aspect ratio of the resist thickness to the pattern width that is targeted, the top pole tip width is limited to the precision of the photolithography. Moreover, the highly developed topography of the top pole tip at the ABS initiates light distortion on the slope of the zero throat insulator during exposing. Hence, as the track width decreases, it becomes progressively more difficult to produce the pole tips to the precision required. To solve this problem, a two-piece structure of the top pole was proposed in U.S. Pat. No. 5,452,164.
The use of a two-piece pole structure facilitates the achievement of a submicron pole tip width at the ABS. The two-piece pole employs a first piece (pole tip) having a very narrow width at the ABS, and a second pole piece connected to the first pole piece and extending to the back region of the head. Thus, the first pole piece defines the narrow track width, and the second pole piece links through the coils and connects to the other (e.g., bottom) pole. The second pole piece of a two-piece pole is made wider at the ABS than the first pole piece due to photolithography limitations. As a result, sharp corners are formed in the second pole piece at the ABS. These corners produce a large fringing magnetic field during recording. The fringing field may adversely affect data recorded on adjacent tracks by erasing or re-writing previously recorded information.
In addition, the two-piece pole structure design proposed in U.S. Pat. No. 5,452,164 has a high sensitivity of non-linear transition shift (NLTS) and overwrites (OVW) to the write current due to a poor control of the pole tip saturation at the ABS. An improved structure of the top pole exhibiting better NLTS and OVW characteristics was proposed in U.S. Pat. No. 5,801,910. In the improved structure, the pole tip has a funnel shape with a long saturation zone localized at the ABS. That saturation zone is generated by one or more break points. However, the funnel-shaped top pole tip is normally formed on the zero throat insulator with uncontrolled light distortion.
It would be desirable to produce a read/write head that allows for greater tolerance control of the width of the top pole at the air bearing surface, that exhibits good NLTS and OVW characteristics, and that eliminates the fringing field effect found in prior art pole structures.
A magnetic recording head includes a writer having a top pole, a shared pole, a first conductive coil and a write gap region. The top pole includes a first top pole piece and a second top pole piece. The second top pole piece is formed at least in part over the first top pole piece. The write gap region is positioned between the top pole and the shared pole and under the first conductive coil. The second top pole piece is recessed from the air bearing surface. A recess is formed in the shared pole and filled with a non-magnetic material. The recess defines a throat height of the magnetic recording head.
The read/write head of the present invention includes a substantially planar first top pole piece, which allows for greater tolerance control of the width of the top pole at the air bearing surface. The first top pole piece has a funnel-shape with a long saturation zone to suppress sensitivity of the NLTS and OVW characteristics to the write current. By recessing the second top pole piece from the air bearing surface, the fringing field effect found in prior art structures is eliminated.